The Basque separatist group Eta's announcement of plans for a permanent ceasefire today received a cautious welcome from the Spanish government.

A statement released to a television station and local newspaper said the group planned to begin a "permanent" ceasefire on Friday, bringing an end to almost 40 years of violence.

Such a move would be the first step towards peace for Eta. The organisation's actions have killed more than 800 people since 1968 in its fight to create an independent state in northern Spain and south-western France.

"The aim of [the ceasefire] is to promote a democratic process in the Basque country and to build a new framework in which our rights as a people will be recognised," the statement said.

The separatist organisation also called on the Spanish and French authorities to "respond positively" to the ceasefire and "leave their repressive ways behind".

The Spanish prime minister, José Luis Rodríguez Zapatero, said he was reacting with "caution" to the statement. Last month, Mr Zapatero said he was optimistic Eta would soon declare a truce.

The ceasefire announcement was welcomed by the Irish government, which has regularly raised the issue of Eta violence with the Spanish government.

It is understood the successful peace process in Northern Ireland influenced negotiations between Eta and the Spanish authorities, with the renouncement of violence by the IRA - with which Eta has had a long relationship - thought to be a major factor.

The Sinn Féin leader, Gerry Adams - who has visited the group regularly over the past decade - called today's announcement "an opportunity of historic proportions".

Eta often uses local Basque media outlets to issue its statements. Today's announcement followed speculation the group could be poised to reveal ceasefire plans.

It has not been involved in a fatal attack since May 2003, when a car bomb killed two police officers in the northern town of Sanguesa. However, it has continued a campaign of relatively low-level violence despite offers by the Spanish government to negotiate.

Earlier this month, the group admitted it had been behind four roadside bombs planted in northern Spain prior to a general strike called by separatists. Nobody was injured.

Many in Spain believe the Madrid bombings of March 11 2004, carried out by Islamist extremists, effectively finished Eta's tactics. Popular revulsion over terrorism has made fatal violence politically unthinkable.

Police action before the bombings saw hundreds of Eta members imprisoned and several attempted bombings foiled.

Last month, tens of thousands of people marched through Madrid, urging the government not to begin peace talks. They called for Eta to be combated through tough police action.

It is classed as a terrorist group by the US and EU, and had previously announced a ceasefire in September 1998. However, that was rescinded in December the following year.